Multiple dense phase risers to maximize aromatics yields for naphtha catalytic cracking

ABSTRACT

Systems and methods for producing aromatics and olefins via catalytic cracking are disclosed. A naphtha feed stream and lift gas stream are fed into one or more dense phase riser reactors, each of which is operated with a high solid volume fraction, a high superficial velocity, high back mixing. The effluent streams from all the dense phase riser reactors is further separated, in a secondary reactor, into a gaseous product stream and a catalyst stream. The catalyst stream is stripped to remove the hydrocarbons absorbed on the catalyst particles. The stripped catalyst is regenerated in a regenerator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/883,069 filed Aug. 5, 2019, which is herebyincorporated by reference in its entirety.

FIELD OF INVENTION

The present invention generally relates to systems and methods forproducing aromatics and olefins. More specifically, the presentinvention relates to systems and methods for producing aromatics andolefins via catalytic cracking naphtha in dense phase riser reactors.

BACKGROUND OF THE INVENTION

BTX (benzene, toluene, and xylene) are a group aromatics that are usedin many different areas of the chemical industry, especially the plasticand polymer sectors. For instance, benzene is a precursor for producingpolystyrene, phenolic resins, polycarbonate, and nylon. Toluene is usedfor producing polyurethane and as a gasoline component. Xylene isfeedstock for producing polyester fibers and phthalic anhydride. In thepetrochemical industry, benzene, toluene, and xylene are conventionallyproduced by catalytic reforming of naphtha.

Over the last few decades, the demand for aromatics, especially BTX, hasbeen consistently increasing. One of the conventional methods ofproducing BTX includes steam cracking hydrocarbon feeds such as naphtha.However, the overall efficiency for this conventional method isrelatively low. Besides aromatics, other products including olefins,which compete with aromatics in the process, are also produced.Furthermore, a large amount of hydrocarbons in the effluent are recycledto the steam cracking unit. As hydrocarbons have to be hydrogenatedbefore they are recycled back to the steam cracking unit, the largeamount of hydrocarbons for recycling can demand a large amount ofhydrogen and energy in the hydrogenation process, resulting in highproduction cost.

Another conventional method for producing aromatics (e.g., BTX) includescatalytic cracking of naphtha in a fluidized bed. However, theseconventional fluidized bed reactors are generally operated with lowaverage solid volume fraction and low gas-solids contact efficiency dueto the limitation of superficial gas velocities in the fluidized bed.Thus, the products of the conventional methods often include a highmethane content produced from thermal cracking of hydrocarbons,resulting in increased production cost for aromatics.

Overall, while methods of producing light olefins exist, the need forimprovements in this field persists in light of at least theaforementioned drawbacks of the methods.

BRIEF SUMMARY OF THE INVENTION

A solution to at least some of the above-mentioned problems associatedwith the production process for aromatics (e.g., BTX) using naphtha asthe feed material has been discovered. The solution resides in a methodof producing aromatics and olefins that includes using one or more densephase riser reactors to catalytically crack naphtha. The superficial gasvelocity in one or more of the dense phase riser reactors issignificantly higher than the conventional methods. This can bebeneficial for at least providing high solid volumetric fraction in eachof the riser reactors, thereby reducing the occurrence of thermalcracking of the naphtha. Additionally, the lift gas used in the densephase riser reactor does not contain steam. Thus, zeolite basedcatalyst, which has higher efficiency than non-zeolite based catalyst,can be used and is not subject to de-alumination by steam. Moreover,this method allows for sufficient back mixing in the dense phase riserreactors, as characterized by wide residence time distribution (RTD)with relative variance of greater than 0.33, resulting in improved BTXto olefins ratio in the effluent from the dense phase riser reactors.Therefore, the method of the present invention provides a technicalsolution to at least some of the problems associated with the currentlyavailable methods for producing aromatics mentioned above.

Embodiments of the invention include a method of producing aromaticsand/or olefins. The method comprises contacting, in a dense phase riserreactor with an average solids volume fraction of at least 0.08, naphthawith catalyst particles under reaction conditions sufficient to producea first product comprising one or more olefins and/or one or morearomatics. The dense phase riser reactor is operated such thatsuperficial gas velocity therein is in a range of 4 to 20 m/s. Themethod further comprises flowing a mixture of the first product, thecatalyst particles, and unreacted naphtha to a cyclone system disposedin a secondary reactor. The secondary reactor is stacked on top of aregenerator. The method further comprises separating, in the cyclonesystem, the first product from the catalyst particles. The methodfurther still comprises stripping, in a stripper disposed in theregenerator, hydrocarbon vapor from the catalyst particles to producestripped catalyst particles. The method further still comprisesregenerating, in the regenerator, the stripped catalyst particles.

Embodiments of the invention include a method of producing aromaticsand/or olefins. The method comprises contacting, in a dense phase riserreactor, naphtha with catalyst particles under reaction conditionssufficient to produce a first product comprising one or more aromaticsand/or one or more olefins. The dense phase riser reactor is operatedsuch that superficial gas velocity therein is in a range of 4 to 20 m/s.The dense phase riser reactor has an internal diameter in a range of 2.0to 2.75 m. The solids volume fraction (SVF) in the dense phase riserreactor is in a range of 0.1 to 0.2. The method further comprisesflowing a mixture of the first product, the catalyst particles, andunreacted naphtha to a cyclone system disposed in a secondary reactor.The secondary reactor is stacked on top of a regenerator. The methodfurther comprises separating, in the cyclone system, the first productfrom the catalyst particles. The method further still comprisesstripping, in a stripper disposed in the regenerator, hydrocarbon vaporfrom the catalyst particles to produce stripped catalyst particles. Themethod further still comprises regenerating, in the regenerator, thestripped catalyst particles.

Embodiments of the invention include a reaction unit for producingolefins and/or aromatics. The reaction unit comprises one or more densephase riser reactors. Each of the dense phase riser reactors comprises ahousing, a feed inlet disposed on a lower half of the housing, adaptedto receive a feed material into the housing, a lift gas inlet disposedon lower half of the housing, adapted to receive a lift gas into thehousing, a catalyst inlet disposed on the lower half of the housing,adapted to receive catalyst into the housing, and an outlet disposed onthe top half of the housing, adapted to release an effluent of the densephase riser from the housing. The reaction unit further comprises asecondary reactor in fluid communication with the outlet of each densephase riser reactor. The secondary reactor comprises one or morecyclones adapted to separate the effluent of the dense phase riser(s)into a gaseous stream comprising gaseous products and a solid streamcomprising the catalyst. The reaction unit further still comprises aregenerator in fluid communication with the secondary reactor, adaptedto receive the solid stream from the secondary reactor and regeneratethe catalyst of the solid stream. The regenerator is in fluidcommunication with the catalyst inlet of each dense phase riser reactor.

The following includes definitions of various terms and phrases usedthroughout this specification.

The terms “about” or “approximately” are defined as being close to asunderstood by one of ordinary skill in the art. In one non-limitingembodiment the terms are defined to be within 10%, preferably, within5%, more preferably, within 1%, and most preferably, within 0.5%.

The terms “wt. %”, “vol. %” or “mol. %” refer to a weight, volume, ormolar percentage of a component, respectively, based on the totalweight, the total volume, or the total moles of material that includesthe component. In a non-limiting example, 10 moles of component in 100moles of the material is 10 mol. % of component.

The term “substantially” and its variations are defined to includeranges within 10%, within 5%, within 1%, or within 0.5%.

The terms “inhibiting” or “reducing” or “preventing” or “avoiding” orany variation of these terms, when used in the claims and/or thespecification, include any measurable decrease or complete inhibition toachieve a desired result.

The term “effective,” as that term is used in the specification and/orclaims, means adequate to accomplish a desired, expected, or intendedresult.

The use of the words “a” or “an” when used in conjunction with the term“comprising,” “including,” “containing,” or “having” in the claims orthe specification may mean “one,” but it is also consistent with themeaning of “one or more,” “at least one,” and “one or more than one.”

The words “comprising” (and any form of comprising, such as “comprise”and “comprises”), “having” (and any form of having, such as “have” and“has”), “including” (and any form of including, such as “includes” and“include”) or “containing” (and any form of containing, such as“contains” and “contain”) are inclusive or open-ended and do not excludeadditional, unrecited elements or method steps.

The process of the present invention can “comprise,” “consistessentially of,” or “consist of” particular ingredients, components,compositions, etc., disclosed throughout the specification.

The term “primarily,” as that term is used in the specification and/orclaims, means greater than any of 50 wt. %, 50 mol. %, and 50 vol. %.For example, “primarily” may include 50.1 wt. % to 100 wt. % and allvalues and ranges there between, 50.1 mol. % to 100 mol. % and allvalues and ranges there between, or 50.1 vol. % to 100 vol. % and allvalues and ranges there between.

Other objects, features and advantages of the present invention willbecome apparent from the following figures, detailed description, andexamples. It should be understood, however, that the figures, detaileddescription, and examples, while indicating specific embodiments of theinvention, are given by way of illustration only and are not meant to belimiting. Additionally, it is contemplated that changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description. Infurther embodiments, features from specific embodiments may be combinedwith features from other embodiments. For example, features from oneembodiment may be combined with features from any of the otherembodiments. In further embodiments, additional features may be added tothe specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing descriptions taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 shows a schematic diagram of a reaction unit for producingaromatics and/or olefins, according to embodiments of the invention; and

FIG. 2 shows a schematic flowchart of a method of producing aromaticsand/or olefins, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Currently, aromatics, especially BTX, and light olefins can be producedby steam cracking or catalytic cracking of naphtha. However, the overallconversion rate to BTX and/or light olefins for steam cracking naphthais relatively low. Furthermore, the production costs for steam crackingnaphtha are high as steam cracking of naphtha produces a large amount ofraffinate, which needs to be hydrogenated before it is recycled back tothe steam cracking unit.

Thus, the large amount raffinate results in high demand for hydrogen andenergy in the hydrogenation process. Conventional processes ofcatalytically cracking naphtha generally have a relatively lowsuperficial gas velocities and extremely high catalyst to oil ratio inthe catalyst bed, which leads to challenges to maintain pressure balancein the reactor. Furthermore, the conventional catalytic cracking ofnaphtha uses steam as lift gas, which prevents using zeolite basedcatalyst, which has a high catalytic efficiency for BTX and lightolefins. The present invention provides a solution to at least some ofthese problems. The solution is premised on a method includingcatalytically cracking naphtha in a reaction unit that comprises one ormore dense phase riser reactors. This method is capable of retaininghigh solid volumetric fraction along with a high superficial gasvelocity in the dense phase riser reactors, thereby reducing the thermalcracking of naphtha and increasing yields of BTX and/or light olefins.Moreover, this method includes sufficient back mixing of the catalystand hydrocarbons in the dense phase riser reactors. Thus, theselectivity to aromatics (e.g., BTX) is increased over conventionalmethods. Additionally, this method uses a lift gas that does not containsteam such that zeolite based catalyst can be used in the reaction unit,resulting in improved BTX and light olefins production efficiency. Theseand other non-limiting aspects of the present invention are discussed infurther detail in the following sections.

A. System for Catalytically Cracking Naphtha to Produce Aromatics andOlefins

In embodiments of the invention, a reaction unit for producing aromaticsand olefins via catalytic cracking of naphtha comprises one or moredense phase riser reactors, a secondary reactor for gas-solidseparation, and a regenerator. With reference to FIG. 1, a schematicdiagram is shown of reaction unit 100 that is configured to producearomatics (e.g., BTX) and/or olefins (e.g., C₂ and C₃ olefins) and withimproved production efficiency and yield of BTX, compared toconventional steam cracking or catalytic cracking processes. Accordingto embodiments of the invention, reaction unit 100 may include one ormore dense phase riser reactors 101 comprising housing 102, feed inlet103, lift gas inlet 104, catalyst inlet 105, and effluent outlet 106. Inembodiments of the invention, dense phase riser reactor 101 is afluidized bed reactor.

In embodiments of the invention, housing 102 is made of carbon steel,refractory, or combinations thereof. Housing 102 is adapted to hostcatalytic cracking of naphtha. According to embodiments of theinvention, feed inlet 103 may be disposed at lower half of housing 102and adapted to receive a feed stream therein. In embodiments of theinvention, the feed stream includes naphtha. In embodiments of theinvention, lift gas inlet 104 is disposed at lower half of housing 102and adapted to receive a lift gas stream in housing 102. In embodimentsof the invention, lift gas inlet 104 may be disposed below feed inlet103. The lift gas stream may include nitrogen, methane, any inert gas,or combinations thereof. In embodiments of the invention, catalyst inlet105 is disposed on lower half of housing 102. Catalyst inlet 105 may beadapted to receive catalyst particles into housing 102. Non-limitingexamples for the catalyst particles may include zeolite. According toembodiments of the invention, the catalyst particles have a particlesize in a range of 75 to 120 μm and all ranges and values there betweenincluding ranges of 75 to 78 μm, 78 to 81 μm, 81 to 84 μm, 84 to 87 μm,87 to 90 μm, 90 to 93 μm, 93 to 96 μm, 96 to 99 μm, 99 to 102 μm, 102 to105 μm, 105 to 108 μm, 108 to 111 μm, 111 to 114 μm, 114 to 117 μm, and117 to 120 μm. The catalyst particles have a density in a range of 1000to 1700 kg/m³ and all ranges and values there between including rangesof 1000 to 1100 kg/m³, 1100 to 1200 kg/m³, 1200 to 1300 kg/m³, 1300 to1400 kg/m³, 1400 to 1500 kg/m³, 1500 to 1600 kg/m³, 1600 to 1700 kg/m³.In embodiments of the invention, catalyst inlet 105 may be disposedabove lift gas inlet 104. According to embodiments of the invention,lift gas inlet 104 is disposed below feed inlet 103 and catalyst inlet105.

In embodiments of the invention, each dense phase riser reactor 101 maybe substantially cylindrical. Dense phase riser reactor 101 may have aheight to diameter ratio in a range of 8 to 27 and all ranges and valuesthere between including ranges of 8 to 9, 9 to 11, 11 to 13, 13 to 15,15 to 17, 17 to 19, 19 to 21, 21 to 23, 23 to 25, and 25 to 27. Inembodiments of the invention, each dense phase riser reactor 101 has aninner diameter in a range of 2.0 to 2.75 m and all ranges and valuesthere between. According to embodiments of the invention, each densephase riser reactor 101 comprises outlet 106 in fluid communication withsecondary reactor 107 such that an effluent of dense phase riser reactor101 flows from dense phase riser reactor 101 to secondary reactor 107.

Effluent from dense phase riser reactor 101 may include unreactednaphtha, aromatics, light olefins, lift gas, spent catalyst particles,and any other by-products. According to embodiments of the invention,secondary reactor 107 is adapted to separate the effluent from densephase riser reactor(s) 101 into a product gas stream and a spentcatalyst stream. The product gas stream may include unreacted naphtha,aromatics, light olefins, lift gas, byproducts, or combinations thereof.Spent catalyst stream may include spent catalyst particles, hydrocarbonsabsorbed on the spent catalyst particles, lift gas, or combinationsthereof.

According to embodiments of the invention, secondary reactor 107comprises secondary reactor housing 108 and one or more cyclones 109adapted to separate the effluent from riser reactor 108 into spentcatalyst particles and product gas. In embodiments of the invention,each cyclone 109 in secondary reactor 107 is single- or multiple-stagecyclone. Each cyclone 109 may be in fluid communication with a dipleg.The dipleg is adapted to transfer catalyst particles from the cyclone tothe dense bed close to the bottom of secondary reactor 107. Inembodiments of the invention, the dipleg for each cyclone 109 is furtherin fluid communication with a splash plate and/or a trickle valve. Thesplash plate and/or trickle valve may be adapted to avoid bypass of gasup the dipleg of a cyclone.

In embodiments of the invention, a bottom end of secondary reactor 107may be in fluid communication with regenerator 110 such that spentcatalyst stream flows from secondary reactor 107 to catalyst regenerator110. In embodiments of the invention, regenerator 110 is adapted tostrip hydrocarbons absorbed on the spent catalyst and regenerate thespent catalyst after the stripping process. Regenerator 110 may befurther adapted to separate flue gas from the catalyst. According toembodiments of the invention, secondary reactor 107 is stacked on top ofregenerator 110 such that the spent catalyst particles can directly flowfrom secondary reactor 107 to regenerator 110 without any additionaldriving force other than gravity.

According to embodiments of the invention, regenerator 110 comprisesstripper 111 configured to strip hydrocarbons absorbed on the spentcatalyst particles. Stripper 111 may comprise a stripping gas sparger112 configured to release stripping gas for contacting the spentcatalyst. Non-limiting examples for the stripping gas can includenitrogen, methane, flue gas, and combinations thereof. Stripper 111 mayfurther comprise stripper internals 113 configured to enhancecounter-current contacting between the down-flowing emulsion phasestream and the up-flowing bubbles stream in fluidized bed strippers.Stripper internals 113 may include disk structured internals, chevronstructured internals, packing internals, subway grating internals, orcombinations thereof. Stripper internals 113 may further comprisestandpipe 114 adapted to transfer catalyst particles from stripper 111to regenerator 110 and a slide valve adapted to control flow rate ofcatalyst particles from stripper 111 to regenerator 110. In embodimentsof the invention, catalyst regenerator 110 further comprises air inlet115 in fluid communication with air sparger 116 that is disposed incatalyst regeneration unit 112 such that air is supplied intoregenerator 110 through air inlet 115 and air sparger 116. According toembodiments of the invention, catalyst regenerator 110 further comprisesone or more cyclones (e.g., cyclone 118) adapted to separate flue gasfrom the catalyst. The flue gas may include the flue gas produced duringthe catalyst regeneration process. According to embodiments of theinvention, catalyst regenerator 110 comprises one or more catalystoutlets 117, each of which is in fluid communication with catalyst inlet105 of each dense phase riser reactor 101 such that regenerated catalystflows from catalyst regenerator 110 to each dense phase riser reactor101. In embodiments of the invention, secondary reactor 107, stripper111, and regenerator 110 are operated with multiple dense phase riserreactors 101.

B. Method of Producing Aromatics and Olefins

Methods of producing aromatics and olefins via catalytic crackingnaphtha have been discovered. Embodiments of the method are capable ofincreasing solid volume fraction in the reaction unit, and minimizingoccurrence of thermal cracking of hydrocarbons compared to conventionalmethods of catalytic cracking. Therefore, the methods may be able tosignificantly improve production efficiency of aromatics and olefinscompared to conventional methods. As shown in FIG. 2, embodiments of theinvention include method 200 for producing aromatics and olefins. Method200 may be implemented by reaction unit 100, as shown in FIG. 1.

According to embodiments of the invention, as shown in block 201, method200 may include contacting, in dense phase riser reactor(s) 101, naphthawith catalyst particles under reaction conditions sufficient to producea first product comprising one or more aromatics and/or one or moreolefins. In embodiments of the invention, the contacting at block 201includes injecting, into dense phase riser reactor 101, the lift gasthrough lift gas inlet 104, naphtha through feed inlet 103, and/orcatalyst through catalyst inlet 105 such that the catalyst particles andthe naphtha make contact with each other and the materials in densephase riser reactor 101 move upwards. In embodiments of the invention,the naphtha at the contacting step of block 201 comprises hydrocarbonswith a final boiling point lower than 350° C. In embodiments of theinvention, first reaction conditions at block 201 may include asuperficial gas velocity (SGV) in a range of 4 to 20 m/s and all rangesand values there between including ranges of 4 to 5 m/s, 5 to 6 m/s, 6to 7 m/s, 7 to 8 m/s, 8 to 9 m/s, 9 to 10 m/s, 10 to 11 m/s, 11 to 12m/s, 12 to 13 m/s, 13 to 14 m/s, 14 to 15 m/s, 15 to 16 m/s, 16 to 17m/s, 17 to 18 m/s, 18 to 19 m/s, and 19 to 20 m/s. The reactionconditions at block 201 may include a reaction temperature of 670 to730° C. and all ranges and values there between including ranges of 670to 675° C., 675 to 680° C., 680 to 685° C., 685 to 690° C., 690 to 695°C., 695 to 700° C., 700 to 705° C., 705 to 710° C., 710 to 715° C., 715to 720° C., 720 to 725° C., and 725 to 730° C. The reaction conditionsat block 201 may further include a reaction pressure of 1 to 3 bar andall ranges and values there between including ranges of 1 to 1.5 bar,1.5 to 2.0 bar, 2.0 to 2.5 bar, and 2.5 to 3.0 bar. The reactionconditions at block 201 may further include an average residence time indense phase riser reactor 101 of 1 to 3 s and all ranges and valuesthere between including ranges of 1 to 1.5 s, 1.5 to 2.0 s, 2.0 to 2.5s, and 2.5 to 3.0 s. The reaction conditions at block 201 may furtherinclude a weighted hourly space velocity in a range of 0.3 to 3 hr⁻¹ andall ranges and values there between including ranges of 0.3 to 0.6 hr⁻¹,0.6 to 0.9 hr⁻¹, 0.9 to 1.2 hr⁻¹, 1.2 to 1.5 hr⁻¹, 1.5 to 1.8 hr⁻¹, 1.8to 2.1 hr⁻¹, 2.1 to 2.4 hr⁻¹, 2.4 to 2.7 hr⁻¹, and 2.7 to 3.0 hr⁻¹.

According to embodiments of the invention, at block 201, a solid volumefraction (SVF) for a fluidized catalyst bed in dense phase riser reactor101 may be in a range of 0.1 to 0.2 and all ranges and values therebetween including ranges of 0.11 to 0.12, 0.12 to 0.13, 0.13 to 0.14,0.14 to 0.15, 0.15 to 0.16, 0.16 to 0.17, 0.17 to 0.18, 0.18 to 0.19,and 0.19 to 0.20. According to embodiments of the invention, thecatalyst of dense phase riser reactor 101 includes zeolite. At block201, each dense phase riser reactor 101 may be operated at a catalystbed bulk density of 120 to 240 kg/m³ and all ranges and values therebetween including ranges of 120 to 130 kg/m³, 130 to 140 kg/m³, 140 to150 kg/m³, 150 to 160 kg/m³, 160 to 170 kg/m³, 170 to 180 kg/m³, 180 to190 kg/m³, 190 to 200 kg/m³, 200 to 210 kg/m³, 210 to 220 kg/m³, 220 to230 kg/m³, and 230 to 240 kg/m³.

According to embodiments of the invention, at block 201, the lift gasand the naphtha are flowed into dense phase riser reactor at avolumetric ratio of 0.4 to 0.8 and all ranges and values there betweenincluding ranges of 0.4 to 0.5, 0.5 to 0.6, 0.6 to 0.7, and 0.7 to 0.8.Each dense phase riser reactor 101 may include a catalyst bed having acatalyst to oil ratio of 10 to 50 (based on weight) and all ranges andvalues there between including ranges of 10 to 12, 12 to 14, 14 to 16,16 to 18, 18 to 20, 20 to 22, 22 to 24, 24 to 26, 26 to 28, 28 to 30, 30to 32, 32 to 34, 34 to 36, 36 to 38, 38 to 40, 40 to 42, 42 to 44, 44 to46, 46 to 48, and 48 to 50.

According to embodiments of the invention, as shown in block 202, method200 further includes flowing an effluent from each dense phase riserreactor 101 including a mixture of the first product, the catalystparticles, and unreacted naphtha to a cyclone system disposed insecondary reactor 107. The effluent from each dense phase riser reactor101 may further include the lift gas. In embodiments of the invention,the flowing at block 202 is propelled by the lift gas. Non-limitingexamples of the lift gas may include nitrogen, methane, any inert gas,steam, or combinations thereof.

According to embodiments of the invention, as shown in block 203, method200 may further comprise separating the first product from the catalystparticles in the cyclone system of secondary reactor 107. In embodimentsof the invention, the separation at block 203 includes gas-solidseparation to produce a gas product stream and a solid catalyst stream.According to embodiments of the invention, the gas product streamcomprises the first product. In embodiments of the invention, the firstproduct includes unreacted naphtha, BTX (benzene, toluene, xylene),light olefins (C₂ and C₃ olefins), lift gas, by-products, orcombinations thereof. The first product may have a BTX to light olefinsweight ratio of 0.25 to 0.45 and all ranges and values there betweenincluding ranges of 0.25 to 0.30, 0.30 to 0.35, 0.35 to 0.40, and 0.40to 0.45. The yield of BTX may be in a range of 13 to 17% and all rangesand values there between including ranges of 13 to 14%, 14 to 15%, 15 to16%, and 16 to 17%. The separating at block 203 may include passing theeffluent of dense phase riser reactor 101 through one or more cyclonesof secondary reactor 107. In embodiments of the invention, the productgas stream comprises 13 to 17 wt. % BTX.

According to embodiments of the invention, as shown in block 204, method200 includes stripping, in stripper 111 disposed in regenerator 110,hydrocarbon vapor from the catalyst particles to produce strippedcatalyst particles. In embodiments of the invention, the hydrocarbonvapor is absorbed on the catalyst particles before the stripping atblock 204. In embodiments of the invention, at block 204, a volumetricratio of stripping gas to catalyst particles is in a range of 0.02 to0.65 and all ranges and values there between including ranges of 0.02 to0.05, 0.05 to 0.08, 0.08 to 0.11, 0.11 to 0.14, 0.14 to 0.17, 0.17 to0.20, 0.20 to 0.23, 0.23 to 0.26, 0.26 to 0.29, 0.29 to 0.32, 0.32 to0.35, 0.35 to 0.38, 0.38 to 0.41, 0.41 to 0.44, 0.44 to 0.47, 0.47 to0.50, 0.50 to 0.53, 0.53 to 0.56, 0.56 to 0.59, 0.59 to 0.62, and 0.62to 0.65.

According to embodiments of the invention, as shown in block 205, method200 includes regenerating, in regenerator 110, the stripped catalystparticles. In embodiments of the invention, at block 205, the catalystparticles are regenerated in the presence of air. The regenerating atblock 205 may be conducted at a regeneration temperature of 680 to 750°C. and all ranges and values there between including ranges of 680 to690° C., 690 to 700° C., 700 to 710° C., 710 to 720° C., 720 to 730° C.,7300 to 740° C., and 740 to 750° C. In embodiments of the invention, theregenerating at block 205 produces regenerated catalyst and flue gas.The flue gas may be separated from the regenerated catalyst incyclone(s) 118. In embodiments of the invention, the regeneratedcatalyst is flowed to each dense phase riser reactor 101 throughcatalyst outlet 117.

Although embodiments of the present invention have been described withreference to blocks of FIG. 2, it should be appreciated that operationof the present invention is not limited to the particular blocks and/orthe particular order of the blocks illustrated in FIG. 2. Accordingly,embodiments of the invention may provide functionality as describedherein using various blocks in a sequence different than that of FIG. 2.

As part of the disclosure of the present invention, a specific exampleis included below. The example is for illustrative purposes only and isnot intended to limit the invention. Those of ordinary skill in the artwill readily recognize parameters that can be changed or modified toyield essentially the same results.

EXAMPLES Example 1 Production of BTX and Light Olefins Via CatalyticCracking

Experiments on the production of BTX and light olefins via catalyticcracking were conducted a in pilot-scale reaction unit of the presentinvention. The dense-phase riser reactor in the pilot-scale reactionunit was operated with high solid volume fractions and high backingmixing to maximize aromatics yields. The composition of the feedstockused in these experiments are shown in Table 1.

TABLE 1 Feedstock composition Normal Iso- Naphthenic paraffin paraffinspecies Aromatics Olefins Others (wt %) (wt. %) (wt. %) (wt.%) (wt. %)(wt. %) 23.16 28.07 33.83 11.7 0.28 2.96

The reaction conditions for the reaction unit included a reactiontemperature of 680° C., a catalyst regeneration temperature 700° C., areaction pressure of 1.50 atm, a catalyst to oil ratio of 30, a weighthourly space velocity (WHSV) of 1.9 h⁻¹, and a catalyst load of 1500 g.The results of the experiments are shown in Table 2.

TABLE 2 Results from the pilot scale experiments with different reactorsDense Phase max Total Dense Phase 3 m max 3 m max 6 m max 6 m max HD 3 mmax HD 3 m max Yield max Olefins Total Yield Olefins Total Yield OlefinsOlefins * BTX CH4 9.66 9.16 9.84 9.62 12.91 12.02 8.37 7.76 C2H4 13.6116.59 16.76 16.37 16.92 16.42 15.51 14.65 C2H4 + C3H6 25.73 33.09 35.0835.24 32.15 35.13 37.27 34.96 C2H4 + C3H6 + C4H8 30.58 40.71 41.03 41.5137.78 42.14 46.41 43.27 BTX 32.84 16.88 23.49 21.92 25.02 18.37 14.7616.68 C2H4 + C3H6 + C4H8 + BTX 63.41 57.59 64.52 63.43 62.80 60.51 61.1759.95 C3H6/C2H4 ratio 0.89 0.99 1.09 1.15 0.90 1.14 1.40 1.39 C2H4 +C3H6 + C4H8/BTX 0.93 2.41 1.75 1.89 1.51 2.29 3.14 2.59 ratio

The results show that high BTX yields can be obtained in a reactoroperated under conditions comprising short contact times, high solidsvolume fractions, and high backmixing in the reactors.

In the context of the present invention, at least the following 17embodiments are described. Embodiment 1 is a method of producingaromatics. The method includes contacting, in a dense phase riserreactor, naphtha with catalyst particles under reaction conditionssufficient to produce a first product containing one or more olefinsand/or one or more aromatics, wherein the dense phase riser reactor isoperated such that superficial gas velocity therein is in a range of 4to 20 m/s. The method further includes flowing a mixture of the firstproduct, the catalyst particles, and unreacted naphtha to a cyclonesystem located in a secondary reactor, wherein the secondary reactor isstacked on top of a regenerator. The method still further includesseparating, in the cyclone system, the first product from the catalystparticles. The method also includes stripping, in a stripper located inthe regenerator, hydrocarbon vapor from the catalyst particles toproduce stripped catalyst particles, and regenerating, in theregenerator, the stripped catalyst particles. Embodiment 2 is the methodof embodiment 1, wherein the dense phase riser reactor has an internaldiameter in a range of 2.0 to 2.75 m. Embodiment 3 is the method ofeither of embodiments 1 or 2, wherein the dense phase riser reactorincludes a fluidized bed with a solids volume fraction (SVF) in a rangeof 0.1 to 0.2. Embodiment 4 is the method of any of embodiments 1 to 3,wherein the stripper and the regenerator are operated with a pluralityof dense phase riser reactors. Embodiment 5 is the method of any ofembodiments 1 to 4, wherein the one or more dense phase riser reactorsare operated using a lift gas selected from the group consisting ofnitrogen, methane, any inert gas, and combinations thereof. Embodiment 6is the method of embodiment 5, wherein the lift gas contains less than10 wt. % steam. Embodiment 7 is the method of any of embodiments 1 to 6,wherein the catalyst contains particles of average diameter in a rangeof 75 to 120 μm. Embodiment 8 is the method of any of embodiments 1 to7, wherein the catalyst has a particle density of 1000 to 1400 kg/m³.Embodiment 9 is the method of any of embodiments 1 to 8, wherein thefirst product contains unreacted naphtha, aromatics, light olefins, liftgas, by-products, or combinations thereof. Embodiment 10 is the methodof any of embodiments 1 to 9, wherein the reaction conditions include areaction temperature in a range of 670 to 730° C. Embodiment 11 is themethod of any of embodiments 1 to 10, wherein the reaction conditionsinclude a weight hourly space velocity of 0.3 to 3 hr⁻¹ and an averageresidence time of 1 to 5 s. Embodiment 12 is the method of any ofembodiments 1 to 11, wherein the dense phase riser reactor includes afluidized bed having a catalyst to oil weight ratio of 10 to 50.Embodiment 13 is the method of any of embodiments 1 to 12, wherein thedense phase riser reactor is operated at a volumetric feed to lift gasratio of 1.25 to 2.5.

Embodiment 14 is a reaction unit for producing aromatics. The reactionunit includes one or more dense phase riser reactors, wherein each ofthe dense phase riser reactors includes a housing and a feed inletlocated on a lower half of the housing, adapted to receive a feedmaterial into the housing. The reaction unit further includes a lift gasinlet located on bottom of the housing, adapted to receive a lift gasinto the housing. The reaction unit still further includes a catalystinlet located at the bottom of the housing, adapted to receive catalystinto the housing. The reaction unit also includes an outlet located ontop of the housing, adapted to release an effluent of the dense phaseriser from the housing. In addition, the reaction unit includes asecondary reactor in fluid communication with the outlet of each densephase riser reactor, wherein the secondary reactor includes one or morecyclones adapted to separate the effluent of the dense phase riser(s)into a gaseous stream containing gaseous products and a solid streamcontaining a catalyst. The reaction unit further includes a regeneratorin fluid communication with the secondary reactor, adapted to receivethe solid stream from the secondary reactor and regenerate the catalystof the solid stream, wherein the secondary reactor is stacked on top ofthe regenerator and the regenerator is in fluid communication with thecatalyst inlet of each dense phase riser reactor. Embodiment 15 is thereaction unit of embodiment 14, wherein the catalyst regeneration unitfurther includes a stripper adapted to strip hydrocarbons absorbed oncatalyst particles of the solid stream using a stripping gas before thecatalyst is regenerated. Embodiment 16 is the reaction unit ofembodiment 15, wherein the stripping gas contains nitrogen, methane,flue gas, or combinations thereof. Embodiment 17 is the reaction unit ofany of embodiments 14 to 16, wherein the regenerator further includesone or more cyclones adapted to separate flue gas from the catalyst.

Although embodiments of the present application and their advantageshave been described in detail, it should be understood that variouschanges, substitutions and alterations can be made herein withoutdeparting from the spirit and scope of the embodiments as defined by theappended claims. Moreover, the scope of the present application is notintended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the above disclosure, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A method of producing aromatics; the method comprising: contacting,in a dense phase riser reactor, naphtha with catalyst particles underreaction conditions sufficient to produce a first product comprising oneor more olefins and/or one or more aromatics, wherein the dense phaseriser reactor is operated such that superficial gas velocity therein isin a range of 4 to 20 m/s; flowing a mixture of the first product, thecatalyst particles, and unreacted naphtha to a cyclone system disposedin a secondary reactor, wherein the secondary reactor is stacked on topof a regenerator; separating, in the cyclone system, the first productfrom the catalyst particles; stripping, in a stripper disposed in theregenerator, hydrocarbon vapor from the catalyst particles to producestripped catalyst particles; and regenerating, in the regenerator, thestripped catalyst particles.
 2. The method of claim 1, wherein the densephase riser reactor has an internal diameter in a range of 2.0 to 2.75m.
 3. The method of claim 1, wherein the dense phase riser reactorcomprises a fluidized bed with a solids volume fraction (SVF) in a rangeof 0.1 to 0.2.
 4. The method of claim 1, wherein the stripper and theregenerator are operated with a plurality of dense phase riser reactors.5. The method of claim 1, wherein the one or more dense phase riserreactors are operated using a lift gas selected from the groupconsisting of nitrogen, methane, any inert gas, and combinationsthereof.
 6. The method of claim 5, wherein the lift gas contains lessthan 10 wt. % steam.
 7. The method of claim 1, wherein the catalystcomprises particles of average diameter in a range of 75 to 120 μm. 8.The method of claim 1, wherein the catalyst has a particle density of1000 to 1400 kg/m³.
 9. The method of claim 1, wherein the first productcomprises unreacted naphtha, aromatics, light olefins, lift gas,by-products, or combinations thereof.
 10. The method of claim 1, whereinthe reaction conditions comprise a reaction temperature in a range of670 to 730° C.
 11. The method of claim 1, wherein the reactionconditions comprise a weight hourly space velocity of 0.3 to 3 hr⁻¹ andan average residence time of 1 to 5 s.
 12. The method of claim 1,wherein the dense phase riser reactor comprises a fluidized bed having acatalyst to oil weight ratio of 10 to
 50. 13. The method of claim 1,wherein the dense phase riser reactor is operated at a volumetric feedto lift gas ratio of 1.25 to 2.5.
 14. A reaction unit for producingaromatics, the reaction unit comprising: one or more dense phase riserreactors, wherein each of the dense phase riser reactors comprises: ahousing; a feed inlet disposed on a lower half of the housing, adaptedto receive a feed material into the housing; a lift gas inlet disposedon bottom of the housing, adapted to receive a lift gas into thehousing; a catalyst inlet disposed at the bottom of the housing, adaptedto receive catalyst into the housing; an outlet disposed on top of thehousing, adapted to release an effluent of the dense phase riser fromthe housing; a secondary reactor in fluid communication with the outletof each dense phase riser reactor, wherein the secondary reactorcomprises one or more cyclones adapted to separate the effluent of thedense phase riser(s) into a gaseous stream comprising gaseous productsand a solid stream comprising a catalyst; and a regenerator in fluidcommunication with the secondary reactor, adapted to receive the solidstream from the secondary reactor and regenerate the catalyst of thesolid stream, wherein the secondary reactor is stacked on top of theregenerator and the regenerator is in fluid communication with thecatalyst inlet of each dense phase riser reactor.
 15. The reaction unitof claim 14, wherein the catalyst regeneration unit further comprises astripper adapted to strip hydrocarbons absorbed on catalyst particles ofthe solid stream using a stripping gas before the catalyst isregenerated.
 16. The reaction unit of claim 15, wherein the strippinggas comprises nitrogen, methane, flue gas, or combinations thereof. 17.The reaction unit of claim 14, wherein the regenerator further comprisesone or more cyclones adapted to separate flue gas from the catalyst. 18.The reaction unit of claim 15, wherein the regenerator further comprisesone or more cyclones adapted to separate flue gas from the catalyst. 19.The reaction unit of claim 16, wherein the regenerator further comprisesone or more cyclones adapted to separate flue gas from the catalyst. 20.The method of claim 3, wherein the dense phase riser reactor is operatedat a volumetric feed to lift gas ratio of 1.25 to 2.5.